Nowadays, an organic EL device attracts attention as a lighting device replacing an incandescent lamp and a fluorescent lamp, and many studies are made.
As used herein, the organic EL device means one in which an organic EL element is stacked on a transparent substrate such as a glass substrate or a transparent resin film.
In the organic EL element, two electrodes in which one or both the electrodes have translucency are opposed to each other, and a light emitting layer made of an organic compound is stacked between the electrodes. The organic EL device emits light by energy of recombination of an electron and a hole that are electrically excited.
The organic EL device is a self-luminous device, and the organic EL device can emit the light having various wavelengths by properly selecting a material for the light emitting layer. The organic EL device is extremely thin compared with an incandescent lamp and a fluorescent lamp, and the organic EL device planarly emits the light. Therefore, there are few restrictions to an installation place.
In order to prevent moisture or oxygen (hereinafter, also referred to as water or the like) from invading into the organic EL element, the organic EL device has a sealing structure that blocks the organic EL element from an external atmosphere.
However, in the case where the organic EL element has the insufficient sealing function, a non-luminous point called a dark spot is generated after a long period of use of the organic EL device.
The dark spot will be described in detail. In the case where the organic EL element has the insufficient sealing function, the water or the like invades into the sealing structure, and the organic EL element is exposed to the water or the like. At this point, when the organic EL element is used (lit), the electrode constituting the organic EL element or an organic compound layer in the vicinity of the electrode interface is partially oxidized, and an insulating oxide layer is formed on the surface. When the oxide layer is formed, the place where the oxide layer is formed is partially insulated. Therefore, the place does not emit the light during the lighting, but the dark spot is formed.
In order to prevent the formation of the dark spot in the organic EL device, it is necessary to surely prevent the water or the like from invading into the organic EL element.
As a technique of preventing invasion of water or the like into the organic EL element, Patent Document 1 is known. Patent Document 1 discloses a technique of providing an organic EL element having a structure in which a first electrode (electrode), an organic compound layer (light emitting layer), and a second electrode (electrode) are sequentially stacked on a base member, and sealing it by overlaying a silicon alloy layer as a sealing layer on the second electrode.